1. Field of the Invention
The present invention relates to a drop detection device or an abnormality detection device for a portable apparatus or like apparatus that can be carried by hand, and more particularly to a drop detection device or an abnormality detection device for protecting the apparatus against possible accidents, such as physical damage to the apparatus, corruption of information transfer, and accidental firing of the apparatus, that could occur due to an impact when the apparatus was dropped or when an abnormal acceleration force was applied to the apparatus.
2. Description of the Related Art
In recent years, portable information processing apparatuses, including portable telephones, have become smaller in size and higher in performance. Such portable electronic apparatuses may be accidentally dropped from the hand while in use and, in view of this, various means have been devised to protect critical constituent elements, i.e., printed wiring boards, of such small-size information processing apparatuses, against impact.
For example, in Nikkei Electronics, Jul. 7th, 2003, pp. 116–124, there is described a structural approach that employs a structure in which, to protect against dropping impact, the printed wiring board is held in position by means of reinforcing ribs and bosses provided on the housing, rather than fixing the wiring board with many screws. Alternatively, a method is employed that fixes the printed wiring board in place by flowing a resin called “underfill” into a gap between the package and the wring board. Further, development of impact resistant solder, etc. is under way.
As portable apparatuses such as portable telephones have come to be equipped with digital cameras, higher functionality and higher performance are demanded for their built-in cameras, calling for a further increase in the number of pixels and the introduction of such features as autofocus and optical zoom. If these features are to be implemented, driving mechanisms for camera modules will inevitably become complex.
Small-size information processing apparatuses such as portable telephones tend to be accidentally dropped or hit against a hard object while in use, because of their small size and light weight. Among others, high-functionality, high-performance camera modules, such as described above, are sensitive to impact. If the camera module is to be designed with impact resistance, the camera module must be made larger in size and heavier in weight. In particular, when the optical zoom feature is incorporated, a lens barrel holding lenses therein is extended and retracted using a cam mechanism; here, if an impact is applied when the lens barrel is in its extended position, often the impact concentrates on the cam mechanism, resulting in breakage of the cam mechanism.
To enhance the impact resistance, it is desirable from the design point of view that the apparatus be designed so that the impact applied to the housing of the camera module will be transmitted, directly to its component parts, as little as possible; for example, to alleviate the impact, impact resistance measures have been proposed, such as mounting the module in such a manner as to be isolated from the frame or protecting the module itself by an elastic member.
Memory cards are finding widespread use in many fields, because of their small size, large capacity, and high operating speed; in particular, removable memory cards are increasingly used in digital cameras, portable game machines, etc. The removable memory card has contacts for connection with an apparatus in which the card is inserted, and in many cases, plate spring-like electrodes are provided on the apparatus side and flat pads are formed on the card in order to facilitate smooth insertion and removal of the card. If such a memory card is accidentally dropped, or if an impact is applied due to a violent motion to the apparatus in which the card is inserted, the power supply may be cut momentarily, and the data being written may be corrupted or the data transfer contacts may be momentarily disconnected (contact lift), resulting an inability to write the data correctly. Accordingly, in applications where correct data transfer is demanded, the above problem is addressed, for example, by reducing the spring constant of the plate spring-like electrodes on the apparatus side, by duplicating the contacts, or by verifying the written data against the original data. Duplication of the contacts may serve to reduce the chance of contact disconnection, but cannot definitely reduce the chance to zero; besides, the duplication involves the problem of increased cost and increased size. On the other hand, the verifying approach entails a reduction in effective write speed and an increase in power consumption. The solutions so far described are approaches from the viewpoint of structure and material.
In technical fields other than the information apparatus field described above, there are also cases where the handling of an apparatus that tends to be dropped accidentally or subjected to an abnormal acceleration force can pose a problem. Portable firearms are an example of such apparatus. For example, when one is using a rifle or the like, one may accidentally drop the rifle or may swing the rifle beyond the tolerable limit specified in the method of use; here, when the rifle is dropped, or when the rifle is subjected to an abnormal impact, the trigger of the rifle may be hit by an object at the spot where the rifle is dropped, causing accidental firing of the rifle. Such accidental firing has long been a problem.